Applying a liquid composition, such as ink, onto a substrate by printing and by other means is well known in the art. Printing of ink may be done to make aesthetically pleasing designs on the substrate. Such designs are desired by the consumer and may increase sales of the product embodying the printed substrate. Alternatively, the substrate may be coated with liquid compositions having desired properties, such as surfactants to increase hydrophilicity, adhesives to join two substrates together, or silicones to promote tactile sensation.
In the printing arts, such as flexography, rotary apparatuses are used for applying various liquid compositions to a travelling substrate. Such apparatuses typically comprise a frame, an axially rotatable anilox roll mounted on the frame, and a reservoir for holding the liquid composition until it is removed from the reservoir by the anilox roll. In the prior art, the reservoir was open to the atmosphere.
One improvement to apparatuses according to the prior art was to provide multiple doctor blades, typically two, contacting the periphery of the anilox roll so that a closed reservoir was formed. As illustrated in U.S. Pat. No. 4,945,832 issued Aug. 7, 1990 to Odom, this arrangement is helpful in preventing splashing of the liquid composition from a reservoir open to the atmosphere.
Various efforts have been made to properly locate the closed reservoir relative to the anilox roll. For example, the aforementioned Odom patent locates the reservoir at the bottom dead center of the anilox roll. U.S. Pat. No. 4,821,672 issued Apr. 18, 1989 to Bruno teaches a laterally mounted reservoir, disposed at the three o'clock position on the anilox roll. However, all such closed reservoirs require complex sealing means to maintain the pressure boundary for the liquid composition. For example, the aforementioned Bruno patent and U.S. Pat. No. 4,481,995 issued Apr. 15, 1986 to Stone both disclose sealing arrangements, for the ends of the anilox roll, which seals are necessary to maintain the pressure boundary of the reservoir.
Yet another problem with such printing apparatuses is the wear and adjustment of the doctor blade which forms part of the pressure boundary of the reservoir and contacts the anilox roll to form an in-running nip. This doctor blade is subject to abrasion from debris entering the nip. Even slight asperities from such debris and routine wear and tear will breach the pressure boundary of the reservoir and cause unintended and undesired loss of ink therefrom.
One approach to this problem has been proposed in U.S. Pat. No. 4,938,133 issued Jul. 3, 1990 to Bock et al., which patent discloses an apparatus to permit easy removal, engagement, and disengagement of the doctor blade. However, this approach is not entirely satisfactory, as the original problem of doctor blade replacement and maintenance still persists.
Yet another problem with the apparatuses according to the prior art, and having either an open reservoir or a closed reservoir, is the complex arrangement necessary to remove the reservoir from its operational position for routine maintenance. Maintenance typically requires draining the reservoir and concomitantly significant downtime. Typically, a hingeably connected reservoir must be removed from its operating position to allow any significant maintenance to be performed. One approach to this problem is suggested in U.S. Pat. No. 4,878,427 issued Nov. 7, 1989 to Washchynsky et al., which discloses an apparatus for removing the anilox roll without tools. However, not all maintenance problems can be corrected by interchanging the anilox roll.
Accordingly, it is an object of this invention to overcome the problems associated with printing apparatuses of the prior art. Particularly, it is an object of this invention to provide a means for minimizing undesired splashing of ink from the reservoir of the printing apparatus. Further, it is an object of this invention to prevent wastage of ink from occurring when ink is removed from the reservoir without being applied onto substrate.
It is also an object of this invention to provide a more reliable means for assuring proper coating of the ink onto the anilox roll so that streaking and fading of the pattern onto the substrate is minimized even at high speed operation. Finally, it is an object of this invention to provide an improved means for separating the reservoir and anilox roll relative to one another, so that downtime is minimized when maintenance occurs and less waste of ink occurs when the reservoir and anilox roll are in the separated position.